Cutter head for phonograph recording



Aug. 30, 1932. R. HEAD 1,874,101

CUTTER HEAD FOR PHONOGRAPH RECORDING Filed July 30, 1929 INVENTOR fioberz f/ead,

BY g ,DW W +M ATTORNEYS Patented Au 30, 1932 UNITED @STATES PATENTOFFICE ROBERT HEAD, OF

TION or nELewAnE ASSIGNOR, ZBY MESNE ASSIGNMENTS, TO

CUTTER HEAD FOR PHONOGRAPH RECORDING Application filed July 30, 1929.Serial No. 882,254.

This invention relates to the art of phonograph recording on blank formsof wax or other suitable material capable of receiving impressions froma vibrating stylus; and more particularly relates to the stylus-bearingcutter'utilized in the actual record-cutting process. I

An object of the invention is to provide a so-called advance ballattachment forthe cutter, the purpose of which is to automaticallyregulate the depth of the cutting groove and thus prevent overcuttingduring record- 1n Tn the recording of acoustical vibrations by means ofimpressions made in blank forms consisting of wax or the like, it iscommon practice to mount the stylus-bearing cutter upon a pivotallysupported arm extending axially in both directions from the point ofsupport. The cutter is mounted at one end of the arm, and suitableweights for counterbalancing the cutter are mounted at the op osite endof the arm. The depth of the cut is regulated by so positioning thebalancing weights that the weight of the cutter overbalances the weightsby a sufficient amount to give a desired depth of out. If the wax formor blank, which receives the cut, is perfectly homogeneous and uniformthruout and presents a perfectly plane surface to the cutting stylus,this method of adjustment will result in approximately constant depth ofcut during the entire recording process.

Record blanks are in general of sufficiently uniform density thruout asto. effect to a negligible extent the uniformity in depth of cut duringrecording. It is a common fault of wax blanks, however, to offer awarped or otherwise uneven surface to the cutter element which, ingeneral, results in varying degrees of penetration of the cuttingstylus.

' Thus where the above described arrangement is utilized for placing thecutter in operative engagement with the record blank, a relatively deepcut will occur as an elevation passes under the stylus and a relativelyshallow cut as a depression passes thereunder. Upon reproduction of arecord cut in this fashion the variations in depth of out causecorresponding variations in 'intensit of the reproduced sound orquavering e ect which is displeasing acoustically.

The present invention provides a device for overcoming this effect byensuring" that the cutting stylus penetrates the blank to asubstantially constant depth at all oints. of the recording surfaceregardless o irregularities in the surface thereof. This device forregulatin depth of out, which is termed an advance all consists of anadjustable support provided with a highly polished spherical orknob-like bearing surface adapted to engage the surface of the record inadvance of the sound groove formed by the cutting stylus and therebypartially support the weight of the cutter. This bearing surface oradvance ball, due to its blunt rounded contour, merely slides upon thesurface of the blank leaving no appreciable impression thereupon. I

The advance ball is situated adjacent the cutting stylus, and isprovided with means for adjusting the height thereof relative to thepoint of the stylus, in this way regulating the depth to which thestylus penetrates into the record. By properly adjusting the weight ofthe cutter carried by the advance ball support, the advance ball may becaused to ride upon the surface of'the record at all times in thismanner causing the cutting stylus to penetrate the wax to asubstantially constant depth at all times including the passage overelevations and depressions.

A detailed description of the advance ball attachment of the presentinvention will be given with reference to the drawing, of which Fig. 1shows in perspective a standard type of electricalcutter of well-knownconstruction having associated therewith the advance ball attachment ofthe presentinvention.

Fig. 2 shows a plan view of the cutter with the advance ball inposition, as viewed from below in Fig. 1.

Fig. 3 shows a side elevational view of the cutter, partly in section,in position for out- CITY, NEW YORK, A CORPORA- ting a record, portionsof the record blank and of the recording machine being properly,

associated therewith to indicate the mode of closure thereof is notrequired in describing the advance ball attachment of the presentinvention. The use of the advance ball attachment described herein is,of course, not limited to the particular cutter structure shown, butmay, with minor modlfications, be applied to any desired type of cutter.

Referring-to the drawing, the cutter comprises a permanent horse-shoemagnet 1, a cutting stylus 2, and a casing 3 encloslng the internalstructure of the cutter such as an armature 25 suitably associated withthe cutting stylus and'an acoustical-frequency current-carrying coil 26,with leads 27 sultably surrounding the same for actuatmg the stylus inaccordance with the sounds to be recorded. A bottom plate 18 isaifixedto the caslng 3 by means of screws 19 for further enclosing theinternal structure of the cutter. Alfixed to one side of the cutter bymeans of screws 24; is a plate 23 provided with a cylindrical lug 4which lug is adapted to fit into a corresponding hole of thepivotallysupported arm of the cutting machine mentioned above, after themanner indicated in Fig. 3.

The advance ball attachment comprises a hinge plate 5 affixed to thecasing 3 by means of screws 6. A bar 7, preferably of metal, ofsufliciently rugged structure and material to be rigid, is pivotallyaiiixed at one end to the hinge plate 6 by means of the pin 8 assingthru suitable holes in the bar and inge plate. The opposite end of thebar 7 projects beyond the cutter as shown in Figs.

1 and 2, and contains a shallow centering groove 16 adapted to receivethe bevelled point 15 of an adjusting screw 9. This adjusting screw 9 isscrew-threaded thru a suitably drilled and screw-threaded portion 14 ofa lug 12 afiixed to the side of the casing 3 by means of screws 13; Theadjusting screw 9 has a knurled head 25 adapted to permit manualoperation thereof for adjusting purposes. The lug 12 has formed integraltherewith an outwardly projecting hook 13 having looped thereabout oneend of a coiled spring 10, the other end-of which is ailixed to the bar7 by means of the pin 11. The spring 10 is a tension spring adapted tomaintain the free end of the bar 7 at all times firmly against; thepoint 15 of the adjusting screw, regardless of the position to which thescrew is adjusted.

The bar 7, at a point adjacent the stylus 2, is provided with aknob-shaped bearing member 17 having a polished surface and a radius ofcurvature suitable for causing the same to ride easily over any slightirregularities in the surface of the record. The

advance ball 17 may be constructed of any suitable material, but it hasbeen found that a sapphire is very well adapted for this purpose, sinceit is a hard material which takes a high polish.

It can be seen from Fig. 1 that the height with the coiled spring merelyhoo ed thereover, together with the pivotal support 8, provides meansfor readily obtaining access to the internal structure of the cutter toreplace the stylus or repair the internal structure. To accomplish this,the sprin 10 may be easily "rasped and unhooked rom the 'hook 13, a terwhich the bar 7 is swung clear of the base-plate 18, thereby permittingthe base-plate to be removed from the casing 3. It is believed that thetwo features discussed immediately above are novel to the presentinvention.

Fig. 3 furnishes an illustration of the manner in which the advance balloperates during the recording process. mounted on the cutting machine byinserting the lug 4 in a corresponding hole in the pivoted arm 21associated with the machine in accordance with well understood practice.Only the portion of the ivoted arm 21 which is adapted to receive t elug 4 is shown in the drawing; the remainder of the armbeing brokenaway, since the method of associating the same with the recordingmachine and the structure of the latter are well known in the art asshown by the patent to Quinby 1,785,047. The advance ball 17 rests uponthe surface of a record 20, a portion of which is shown in section. Theweight of the cutter is adjusted to cause the stylus 2 to penetrate theblank until the advance ball 17 rests upon the surface thereof the depthof the out being, of' course, determined by the adjustment of theadjusting screw 9 after the manner described above. The rotation of theblank and the radial advance of the cut ter is such that the advanceball 17 always rides in advance of the sound grooves 22 formed by thecutting stylus 2.

I claim:

1. The combination with a phono raph record cutter including a stylus,o? a rigid bar extending across the base thereof adjacent said stylus,means pivotally aflixing one end of said bar to said cutter, the otherend of said bar projecting beyond said cutter and having longitudinallyformed therein a shallow centering groove for reception of the bevelledpoint of an adjusting screw, said adjusting screw being screw-threadedthru a lug aflixed to said cutter, said lug having formed thereon anoutwardly exof the advance ball 17, relative to the point The cutter istending hook adapted for fastening one end of a coiled spring connectedto said bar for holdin the same against said adjustin screw or alladjusting positions thereof, an a knob-shaped support carried by saidbar adjacent said stylus and adapted to engage the surface of a recordin advance of the sound groove formed by said stylus.

2. The combination with a phonograph record cutter including a stylus,of a rigid bar having one end pivotally affixed to said cutter andextending across the base thereof and projecting beyond the same, saidprojecting end having longitudinally formed therein a shallow centeringgroove for reception of one adjusting screw point, said screw beingscrew-threaded thru a lug affixed to said cutter, means resilientlymaintaining said bar against the screw in all adjusting positions, andsaid bar being provided with a smooth rounded support adjacent saidstylus adapted to en age a rec-- 0rd, said adjusting screw provi ingmeans for regulating the penetration depth of said stylus into saidrecord.

3. The combination with a phonograph record cutter including a stylusand having a removable base plate for aifording access to the internalstructure thereof, of a rigid bar pivotally afiixed at one end to saidoutter and extending across the base thereof to project beyond the same,said projecting end having longitudinally formed therein a shallowcentering groove adaptedto receive the point of an ad usting screw,screw-threaded thru a lug aflixed to said cutter, and means forresiliently maintaining said bar against said screw for all adjustinpositions thereof, said bar being provide with a rounded supportadjacent said stylus adapted to engage the surface of a record, saidresiliently maintaining means comprising a coiled spring aflixed at oneend to said bar and having the other end looped about an outwardlyextendin hook affixed to said cutter, whereby said bar may be unfastenedat one end and swung clear of said base plate to facilitate removal ofthe same.

In testimony whereof I affix my signature.

. ROBERT HEAD.

